Citrus Management and Diagnostic Software

J. J. Ferguson, M. B. Thomas, H. W. Beck, J. H. Crane and F. S. Zazueta

Abstract

Citrus diagnostic and management software have been developed to improve production practices and diagnosis of diseases, disorders and pest damage in Florida. Citrus databases contain extension documents and applications programs on citrus production and management. A diagnostic key identifies the major fungal diseases of citrus foliage and fruit in Florida, along with hypertext-linked descriptions and graphic displays of symptoms, maps of geographic occurrence, diagrams of disease development and management strategies. A larger CD-ROM diagnostic system, including diseases, disorders and pests of citrus and tropical fruits, links screen images to summary documents graphic displays and hypertext-linked extension publications as well as current control methods. In other management programs, citrus spray mixtures can be calculated as can the relative mobility of pesticides in specific soil types, especially in response to irrigation, evapotranspiration, soil properties and other factors. Dilution rates for liquid and dry fertilizer injected into irrigation water can be determined. Irrigation systems can be designed and scheduled. Individual citrus trees can be evaluated, surveyed and mapped. Annual net returns and the cost of tree mortality can be calculated.

Keywords: subtropical and tropical fruit crops, Florida

Introduction

Computer software, including simulation models and expert systems, has been developed to improve disease and pest management of fruit crops, particularly deciduous fruit crops. Simulation models, based on weather conditions and field estimates of inoculum potential, predict the incidence of fire blight of pears (Jacquart-Ramon et al, 1987) and downy mildew of grapes (Blaise and Gessler, 1992; Rosa et al., 1993). Other programs rely on monitored meteorological data from orchards (Laurenson and Manktelow, 1992) and on both monitored and forecast weather (Beresford and Spink, 1992) to predict the development of apple black spot. Large, integrated expert systems for apples contain interacting modules on disease potential, pest injury, insect threshold levels and pesticide selection, application rates, spray intervals, compatibility and days to harvest (Travis et al., 1992; Haley et al., 1990). Other expert systems, based on symptom location in plant tissue, diagnose 120 disorders of peach and nectarine trees (Plant et al., 1989); enhance the integration of pesticides with arthropod biological control on tree crops (Messing and Croft, 1990) and integrate insect and disease management on hazelnuts (Drapek et al., 1990). Hypertext systems have also been utilized in CD-ROM agricultural databases (Beck et al., 1994) and to describe over 600 cultivars of peach and nectarines and their performance in the southeastern United States (Okie, 1993). Although few large simulation models and expert systems have been developed for subtropical and tropical fruit crops, agricultural databases and software for management of citrus and tropical fruits have been developed in Florida and will be reviewed in this paper.

Citrus Databases

The Florida Agricultural Information Retrieval System (FAIRS) project (Beck et al., 1994) has produced 10 CD-ROM disks to date, with each disk holding up to 680 megabytes of information on commercial agricultural production and homeowner horticulture, organized into handbooks containing extension publications. A single handbook may contain over 100 extension documents. Additional CD-ROM disks on citrus, soil management, agricultural safety and selection of landscape trees have also been released. The Citrus Disk contains information on: pest management; grove management; laws, regulations and safety standards; rootstocks and scions; new plantings; irrigation and water management; nutrition; cold protection; pesticide application and safety; tree size management; equipment and machinery.

Diagnostic Software

CITPATH, (Ferguson et al., 1995) a computerized diagnostic key and information system, was developed to identify the five major fungal diseases of citrus foliage and fruit in Florida: Alternaria brown spot of mandarins, caused by Alternaria alternata (Fr.:Fr.)Keissl.pathotype citri Solel.; greasy spot, caused by Mycosphaerella citri Whiteside; melanose, caused by Diaporthe citri Wolf; Phytophthora brown rot of fruit, caused by Phytophthora nicotianae Breda de Haan; postbloom fruit drop, caused by Colletotrichum acutatum Simmonds; and sour orange scab, caused by Elsinoe fawcetti Bitanc. And Jenk. The diagnostic key poses questions about distinctive visual disease symptoms, requiring a yes or no answer. After the primary symptoms are identified and the disease determined, additional symptoms not included in the key are described, along with suggested reference to the hypertext program for further information. The information base provides hypertext-linked descriptions and graphic displays of symptoms, diagrams of seasonal disease development, pathogen cycles and management strategies, with reference to chemical control methods detailed in the current Florida Citrus Pest Management Guide. Lists of citrus cultivars susceptible to specific diseases and diseases affecting specific cultivars are included. Developed for commercial growers, county extension programs, citrus horticulture classes and master gardeners, this software is available for MS-DOS based computers and on CD-ROM disks containing other citrus databases. CITPATH has also been used as a model to develop a larger CD-ROM based interactive diagnostic program that includes major diseases, disorders and pest problems of citrus (CIT Xpert) and tropical fruit (TFRUIT Xpert) (Thomas et al., 1995).

CIT Xpert includes all citrus cultivars grown commercially in Florida. TFRUIT Xpert includes avocado, 'Tahiti' lime (considered a tropical fruit crop in Florida), mango, carambola, lychee and papaya. CIT Xpert and TFRUIT Xpert were developed using a diagnostic/prescriptive paradigm in which the user is asked to identify symptoms or recognizable characteristics of an unknown problem by morphological region of the tree ( canopy, blossoms, fruit, leaves, twigs, budunion, rootstock, etc.) Symptoms are first identified according to broad symptom class (change in color and shape, presence of insects, etc.). By choosing more specific symptoms (wilting, chlorosis, necrosis, wood staining, fibrous root decay, etc.), the user proceeds through the decision process with the aid of graphic displays (170 and 200 slides of symptoms for CIT XPERT and TFRUIT Xpert, respectively), pop-up menus, dialogue boxes, control methods and extension publications. The final goal is to generate either a single conclusion or a list of possible conclusions that successfully match the symptoms selected by the user. When the causal agent is identified, the user can browse summary documents and retrieve information that may assist the user in confirming the conclusion before utilizing the hypertext function and linking to more detailed extension documents. All summary documents and extension documents can be printed. Both systems are distributed on CD-ROM as part of the Florida Agricultural Information Retrieval System (FAIRS).

Management Software

Pesticide application rates and movement of pesticides in selected soils are addressed in software of different levels of complexity. CITMIX (Fasulo, 1986) calculates different pesticide and or oil concentrations in English units for spray applications on citrus trees of different heights, using different recommended pesticide concentrations per unit volume in spray tanks of different volumes. PESTICIDAL SPRAY CALCULATIONS (Stanley and Price, 1984) is more specific, calling for a specified amount of known, formulated product per unit volume; a specified amount of formulated product and active ingredient per unit area. Equipment application rates per unit area are requested and can be calculated, if unknown. English units of measurement are used, with metric units available for liquid formulations less than 0.94 liters and dry formulations less than 227 grams. CHEMICAL MOVEMENT IN LAYERED SOILS (Nofziger and Hornsby, 1987) estimates the location of the peak concentration of non-polar organic chemicals as they move through a soil (with up to 20 horizons) in response to downward movement of water and the concentration of each chemical in the soil for up to 15 years. CHEMRANK (Nofziger et al., 1988) compares different organic chemicals in terms of their relative likelihood to leach past a specified soil depth into groundwater. Key environmental-fate properties of the chemicals, soil properties, evapotranspiration and water inputs are needed, some of which are provided for Florida soils.

Programs have been developed to identify nutrient deficiencies and to calculate inputs for liquid and dry fertilizers in greenhouse fertigation programs. NUTDEF (Ingram and Yeager, 1986), designed to help identify nutrient deficiency symptoms in woody ornamental plants, can also be used for citrus. The relative mobility of nitrogen, potassium, phosphorus and magnesium and immobility of iron, manganese, zinc, copper, boron, sulfur, calcium and molybdenum and patterns of leaf chlorosis are used to identify nutrient deficiencies. SOLUFERT (Yeager and Ingram, 1986a) calculates the dilution ratio needed to obtain the desired concentration of liquid fertilizers containing nitrogen, phosphorus, or potassium in irrigation water. Fertilizer analysis, parts per million of nitrogen, phosphorus or potassium, the weight/volume ratio of the fertilizer and the dilution ratio of the injector are required to determine 1)the dilution ratio needed to achieve desired parts per million of a fertilizer element in the irrigation water, 2) the dilution of the concentrated fertilizer before injection. 3)the analysis of solution fertilizer to be used with the given dilution ratio to obtain the desired parts per million of a fertilizer element in the irrigation water. FERTDRY (Yeager and Ingram, 1986a) performs a similar function when dry fertilizers are dissolved and injected into irrigation water, with an additional option for using fertilizer compounds like ammonium chloride, potassium nitrate, etc. CITRUS IRRIGATION SCHEDULING (Ayers and Ferguson, 1983) requires rainfall, temperatures, soil water holding capacity, and desired water depletion to predict the projected date that irrigation or rainfall will be needed to forestall tree stress. WATER MANAGEMENT UTILITIES (Zazueta and Smajstrla, 1994) consists of over 40 programs for trickle and turf irrigation system design, management, evapotranspiration, drainage, well hydraulics, runoff estimation, channel design and soil conservation.

Grove management programs develop grove inventories, production costs and incomes. DECISION AIDS FOR CITRUS GROWERS (Muraro et al, 1987) contains two programs that 1) uses information on fruit cultivar, prices, annual fruit yield and costs to calculate annual net returns and accumulated discounted net returns for establishing a new grove 2) uses fruit prices, grove care costs, yields and discount or capitalization rates to determine the value of a particular tree loss. The GROVE RECORDS SYSTEM (Muraro et al., 1983) records production costs, with summaries on a monthly, quarterly or other basis; provides input on harvesting costs; reports gross revenue and net income statements. CITRUS SURVEY AND MAPPING (Oswalt, 1985) allows the user to select up to 15 labels to describe citrus trees in a grove, including cultivar, bearing potential, size, age, vigor, stress, etc. and to summarize and print maps of the planting.

System Requirements

General requirements for the above software include: a computer with at least a 386SX processor; DOS 5.0 or higher; 4Mb RAM or better; a SuperVGA card with at least 512K of RAM (VESA standard); a hard drive with at least 4Mb of free space; a CD-ROM drive (for the FAIRS /CD-ROM disks); a mouse. Outprint can be printed for most programs. Specific information on each the programs discussed can be obtained by ordering the University of Florida Resource Catalog at IFAS Software Support, University of Florida, PO Box 110340, Gainesville, Fl 32611-0340, Phone:352-392-7853.

References

Ayers, D. H. and F. Ferguson, F. S. 1983. Citrus irrigation scheduling. Univ. Fl. Coop. Ext. Ser. Cir. 012, Gainesville, Fl.

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